The present invention provides an apparatus for injecting gas into a vessel. It has particular, but not exclusive application to apparatus for injecting a flow of gas into a metallurgical vessel under high temperature conditions. Such metallurgical vessel may for example be a smelting vessel in which molten metal is produced by a direct smelting process.
A known direct smelting process, which relies on a molten metal layer as a reaction medium, and is generally referred to as the HIsmelt process, is described in International application PCT/AU96/00197 (WO 96/31627) in the name of the applicant.
The HIsmelt process as described in the International application comprises:
(a) forming a bath of molten iron and slag in a vessel;
(b) injecting into the bath:
(i) a metalliferous feed material, typically metal oxides; and
(ii) a solid carbonaceous material, typically coal, which acts as a reductant of the metal oxides and a source of energy; and
(c) smelting metalliferous feed material to metal in the metal layer.
The term xe2x80x9csmeltingxe2x80x9d is herein understood to mean thermal processing wherein chemical reactions that reduce metal oxides take place to produce liquid metal.
The HIsmelt process also comprises post-combusting reaction gases, such as CO and H2 released from the bath in the space above the bath with oxygen-containing gas and transferring the heat generated by the post-combustion to the bath to contribute to the thermal energy required to smelt the metalliferous feed materials.
The HIsmelt process also comprises forming a transition zone above the nominal quiescent surface of the bath in which there is a favourable mass of ascending and thereafter descending droplets or splashes or streams of molten metal and/or slag which provide an effective medium to transfer to the bath the thermal energy generated by post-combusting reaction gases above the bath.
In the HIsmelt process the metalliferous feed material and solid carbonaceous material is injected into the metal layer through a number of lances/tuyeres which are inclined to the vertical so as to extend downwardly and inwardly through the side wall of the smelting vessel and into the lower region of the vessel so as to deliver the solids material into the metal layer in the bottom of the vessel. To promote the post combustion of reaction gases in the upper part of the vessel, a blast of hot air, which may be oxygen enriched, is injected into the upper region of the vessel through the downwardly extending hot air injection lance. To promote effective post combustion of the gases in the upper part of the vessel, it is desirable that the incoming hot air blast exit the lance with a swirling motion. To achieve this, the outlet end of the lance may be fitted with internal flow guides to impart an appropriate swirling motion. The upper regions of the vessel may reach temperatures of the order of 2000xc2x0 C. and the hot air may be delivered into the lance at temperatures of the order of 1100-1400xc2x0 C. The lance must therefore be capable of withstanding extremely high temperatures both internally and on the external walls, particularly at the delivery end of the lance which projects into the combustion zone of the vessel. The present invention provides a lance construction which enables the relevant components to be internally water cooled and to operate in a very high temperature environment.
According to the invention there is provided apparatus for injecting gas into a vessel, including:
a gas flow duct extending from a rear end to a forward end from which to discharge gas from the duct;
an elongate central tubular structure extending within the gas flow duct from its rear end to its forward end;
a plurality of flow directing vanes disposed about the central tubular structure adjacent the forward end of the duct to impart swirl to a gas flow to the forward end of a duct, the forward end of the central structure and the forward end of the duct co-acting together to form an annular nozzle for flow of gas from the duct with swirl imparted by said vanes;
cooling water passages within the central tubular structure for flow of cooling water forwardly through the central structure from its rear end to its forward end and to internally cool that forward end and thence to return back through the central structure to its rear end.
The forward end of the duct may be formed as a hollow annular tip formation and the gas flow duct may include duct tip cooling water supply and return passages for supply of cooling water forwardly along the duct into the duct tip and return of that cooling water back along the duct.
The interior peripheral surface of the duct may be lined with refractory material.
Preferably the central tubular structure defines a central water flow passage for flow of water forwardly through that structure directly to the forward end of the central structure and an annular water flow passage disposed about the central passage for return flow of water from the forward end of the central structure back to the rear end of that structure.
The central tubular structure may comprise a central tube providing the central water flow passage and a further tube disposed around the central tube to define said annular water flow passage between the tubes.
Preferably the central structure includes a heat insulating outer shield to retard heat transfer from gas in the gas flow duct into the cooling water passages in the central structure.
The heat insulating shield may be comprised of a plurality of tubular segments of heat insulating material disposed end to end to form the heat shield as a substantially continuous tube extending from the rear end to the front end of the central structure about an annular air gap disposed immediately within the heat shield.
Said air gap may be formed between the tubular heat shield and the further tube defining the outer wall of the annular water return flow passage.
Preferably said tubular segments of the heat shield are supported to accommodate longitudinal expansion of each segment independently of the other such segments.
The forward end of the central structure may include a domed nose portion provided internally with a single spiral cooling water passage to receive water from the central water flow passage in the central structure at the tip of the nose and direct that water in a single flow around and backwardly along the nose to cool the nose with a single coherent stream of cooling water.
The apparatus may include a gas inlet for introduction of hot gas into the rear end of the duct, the gas inlet comprising a refractory body defining a first tubular gas passage aligned with and extending directly to the rear end of the duct and a second tubular gas passage transverse to the first passage to receive hot gas and direct it to the first passage so that the hot gas and any particles entrained therein impinge on refractory wall of the first passage, the gas flow undergoing a change of direction in passing from the first passage to the second passage.
The first and second gas flow passages may be essentially normal to one another.
The central tubular structure may extend centrally through the first gas flow passage of the gas inlet means and rearwardly beyond the gas inlet. The rear end of the central structure may then be located rearwardly of the gas inlet and be provided with water couplings for the flow of cooling water to and from the central structure.
The invention also provides apparatus for injecting gas into a vessel, including:
a gas flow duct extending from a rear end to a forward end from which to discharge gas from the duct;
an elongate structure extending centrally within the forward end of the duct such that gas flowing through the forward end of the duct will flow over and along the central structure;
a plurality of flow directing vanes disposed about the central structure adjacent the forward end of the duct to impart swirl to a gas flow to the forward end of a duct, the forward end of the central structure and the forward end of the duct co-acting together to form an annular nozzle for flow of gas from the duct with swirl imparted by said vanes; and
a cooling water passage within the central structure for flow of cooling water forwardly to its forward end and to internally cool that forward end;
wherein the forward end of the central structure includes a domed nose portion provided internally with a single spiral cooling water passage to receive water from the central water flow passage in the central structure at the tip of the nose and direct that water in a single flow around and backwardly along the nose to cool the nose with a single coherent stream of cooling water.
The invention further provides apparatus for injecting gas into a vessel, including:
a gas flow duct extending from a rear end to a forward end from which to discharge gas from the duct;
an elongate structure extending centrally within the forward end of the gas flow duct such that gas flowing through the forward end of the duct will flow over and along the central structure;
a plurality of flow directing vanes disposed about the central tubular structure adjacent the forward end of the duct to impart swirl to a gas flowing to the forward end of a duct, the forward end of the central structure and the forward end of the duct co-acting together to form an annular nozzle for flow of gas from the duct with swirl imparted by said vanes;
cooling water passages within the wall of the duct and the central structure for water cooling both the duct and the central structure; and
a gas inlet for introduction of hot gas into the rear end of the duct, the gas inlet comprising a refractory body defining a first tubular gas passage aligned with and extending directly to the rear end of the duct and a second tubular gas passage transverse to the first passage to receive hot gas and direct it to the first passage so that the hot gas and any particles entrained therein impinge on refractory wall of the first passage, the gas flow undergoing a change of direction in passing from the first passage to the second passage.